At least 24,000 people are believed to have made the journey along the Balkans migration trail since European leaders declared the route shut in early March, highlighting how migration continues despite the construction of several fences along borders in eastern and central Europe.

On 9 March the president of the European council, Donald Tusk, declared that “irregular flows of migrants along western Balkans route have come to an end”, after the closure of a humanitarian corridor that funnelled asylum seekers from Greece to Germany and the erection of fences along parts of the Macedonian, Hungarian and Austrian borders.

But although this brought migration numbers down considerably, since 9 March 24,790 people are estimated to have passed through Serbia, a key waypoint on two major migration routes across eastern Europe, according to Guardian analysis of daily records and estimates by the UN refugee agency.

During the same period, 21,231 are recorded as having reached Austria, the last stop on the trail to Germany. This is roughly a tenth of the total during the equivalent timeframe in 2015, but already exceeds the annual total for 2013, and is more than three times greater than 2012’s annual figure.

Many enter Europe through Bulgaria instead of taking boats from Turkey to the Greek islands, where new arrivals are now detained after landing. Those stranded in Greece since detentions began in March sometimes pay smugglers to take them to the Greek mainland and then reach Macedonia on foot, since Macedonia’s new fence does not line the whole border.

“Right now it’s heaven for the smugglers,” said Tareq Ahmed, a 26-year-old Syrian carpenter who set off from northern Greece this week. “Europe is giving smugglers a lot of work.”

Migration through the Balkans is being driven in part by the desperation of the 57,000 people stuck in Greece, most of whom are living in squalid camps. EU member states have promised to relocate all of them, but the system is working so slowly that only 2,681 refugees have been sent to other countries – encouraging many of the rest to smuggle themselves northwards instead.

EU and Turkey restart talks over migrant pact

Read more

“I don’t want to wait here for a year to get just my first appointment [for an asylum interview], so that’s why I’m going to the smugglers,” said Ahmed, who spoke to the Guardian on the day he set off for Macedonia. “If they promised to move us by next March, no one would go with the smugglers. But we haven’t even got our first appointments. We’re Syrians, we’re used to working, we don’t like to sit and do nothing.”

On Tuesday the areas lining the Greek side of the border were covered with the discarded belongings of people who crossed into Macedonia in recent months. In the undergrowth next to the border were sleeping bags, clothing, empty sardine tins and shoes, including a toddler’s trainer.

Migration researchers say that although the closure of the Balkans humanitarian corridor has reduced migration numbers, it has forced many people to seek more dangerous routes to northern Europe.

A child’s shoe lies in the undergrowth that separates Greece and Macedonia. Photograph: Patrick Kingsley for the Guardian

Gauri van Gulik, Amnesty International’s deputy Europe director, said: “Shutting a border like in Macedonia doesn’t mean closing a route for refugees and migrants; it just means more business for exploitative smugglers, more dangerous routes, and more suffering for people who need protection and care. Instead of laying more razor wire and erecting ever higher fences, Europe’s leaders should end their head-in-the-sand politics and provide meaningful, sustainable solutions.”

Raed, a 26-year-old from Damascus, said: “I was caught by the Macedonians and I told them I had a health issue in my stomach so they shouldn’t kick me there. And after that they kicked me only there.”

This treatment is no deterrent for some migrants, who have often experienced far worse traumas to reach Greece, and who will try repeatedly until they manage to enter Macedonia.

At a transit camp in northern Greece for migrants who have been caught trying to enter Macedonia, one of the camp’s only permanent residents said he saw some people return to the camp several times, undeterred by each failed attempt. “I’ve seen one family come and go 10 times,” he said.

Sitting beside him, an Iranian woman added: “I’ve already tried twice and been taken back here twice. And I’ll try again and again.”